Cooling abnormality detection system for electronic equipment

ABSTRACT

An excess heat abnormality detection and alarm system for external electronic equipment includes a protection unit containing a timer for counting a predetermined period of time and outputting a time output signal, a temperature measuring means for causing temperature sensors to measure the temperatures of the electronic components, a first and second abnormal temperature discriminating means, the first abnormal temperature discriminating means being operated for a predetermined period of time set in the timer means. The first abnormal temperature discriminating means identifies or discriminates one of the temperatures measured by the temperature measuring means as an abnormal temperature. A second abnormal temperature discriminating means operated after a predetermined period of time set in the timer means distinguishes between the two temperatures measured by the temperature measuring means. The abnormality alarm means receives an abnormality signal from the first and second abnormal temperature discriminating means and generates a stop signal, which controls the power supplied to each of the external electronic components.

This application is a division of application Ser. No. 07/802,694, filedDec. 5, 1991 now Pat. No. 5,174,364 which is a continuation ofapplication Ser. No. 07/409,742 filed Sep. 20, 1989 now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to a cooling abnormality detection systemfor electronic equipment and, more particularly, to a coolingabnormality detection system for electronic equipment which preventsreliability degradation and breakdown of the electronic equipment due toheat.

In recent years, large scale integration and a higher packing density ofcircuit elements have progressed in electronic equipment such ascomputers to improve performance. Along with this trend, heat generatingdensity inside the equipment increased, and electronic equipmentfrequently employs a cooling system using a liquid coolant. A typicalconventional cooling system employs a flat plate through which a liquidcoolant flows, to cool the electronic equipment through this flat plate.In this system, a temperature sensor or element having an equivalentfunction is arranged in an element or in electronic equipment. An outputfrom this sensor is monitored to prevent reliability degradation orbreakdown of electronic elements and equipment due to heat.

FIG. 1 is a block diagram showing an arrangement of a conventionalcooling abnormality detection system for cooling electronic equipmentserving as a heating element by using the liquid coolant.

Referring to FIG. 1, reference numeral 11 denotes a cooling device; 12,a protection unit; 13, a heat exchanger for re-cooling the liquidcoolant whose temperature is increased upon cooling of electroniccomponents 43; 14, a tank for absorbing an increase/decrease in volumeof the liquid coolant upon temperature change; 15, a pump forcirculating the liquid coolant to electronic equipment 40; 16, an outletport for supplying the liquid coolant to the electronic equipment 40;and 17, an inlet port for receiving the liquid coolant from theelectronic equipment 40. The protection unit 12 sends a start or stopcommand to the heat exchanger 13 and the pump 15 through operationcommand lines 20. Reference numeral 23 denotes a flowmeter for measuringa flow rate of the liquid coolant during the operation of the pump. Theflowmeter 23 informs the protection unit 12 of an abnormality through anabnormality detection line 25 when the actual flow rate is lower than apredetermined rate during the operation of the pump. Reference numeral41 denotes an operation control unit for starting/stopping power supplyto the electronic components 43; 18, a cooling piping forinterconnecting the cooling device 11 and the electronic equipment 40;and 30, an abnormality signal line for signaling the abnormality of thecooling device 11 to the operation control unit 41. Reference numeral 42denotes a temperature measuring the unit for measuring temperatures oftemperature sensors 44 (AD590 or AD592 available from Analog DevicesInc.) respectively arranged inside the electronic components 43; and 33,a temperature abnormality signal line for signaling a temperatureabnormality from the temperature measuring unit 42 to the protectionunit 12.

With the above arrangement, when the flowmeter 23 detects a decrease ina circulating flow rate of the liquid coolant, which disables continuouscooling in the cooling device 11, the protection unit 12 drives theabnormality signal line 30 and sends an abnormality signal to theoperation control unit 41. Thereafter, the operation control unit 41stops power supply to the electronic components 43, thereby preventingreliability degradation or breakdown of the electronic components 43 dueto heat.

When the temperature measuring unit 42 detects that power is supplied tothe electronic components 43 through power signal lines (not shown)under the control of the operation control unit 41, the temperaturemeasuring unit 42 starts measuring the temperatures of the temperaturesensors 44. The temperature measuring unit 42 determines whether themeasured temperatures exceed a predetermined temperature. Thepredetermined temperature is set to be a temperature which has almost noinfluence on the reliability of the electronic components 43.

When the temperature of one of the electronic components 43 exceeds thepredetermined temperature, the temperature measuring unit 42 determinesan abnormality and informs the protection unit 12 of an abnormalitythrough the temperature abnormality signal line 33. When the protectionunit 12 receives the abnormality signal through the temperatureabnormality signal line 33, it immediately informs the operation controlunit 41 of an abnormality through the abnormality signal line 30.Thereafter, the operation control unit 41 stops power supply to theelectronic components 43, thereby preventing reliability degradation orbreakdown of the electronic components 43 due to heat.

In the above temperature abnormality detection, when the temperaturemeasuring unit 42 determines that the measurement results exhibit hightemperatures which exceed the highest rated temperature, the temperaturemeasuring unit 42 informs the protection unit 12 of a "temperaturesensor abnormality" through the temperature abnormality signal line 33.In a normal operation, a criterion for determining an abnormality ofeach temperature sensor 44 is set as a temperature higher by 20° C. to50° C. than the predetermined temperature for determining an abnormalityin the electronic components 43.

In this manner, when abnormality data from the flowmeter 23 or thetemperature measuring unit 42 is signaled, the protection unit 12informs the operation control unit 41 of an abnormality, and causes itto stop power supply to the electronic components 43, thereby preventingreliability degradation or breakdown of the electronic components 43 dueto heat.

The conventional cooling abnormality detection system has the followingdrawbacks.

(1) When an abnormal flow rate of the liquid coolant is detected by theflowmeter, the protection unit stops power supply to the electroniccomponents upon detection of an abnormal flow rate of the liquid coolantby the flowmeter. Therefore, even if a flow rate is normal, when a flowrate of the liquid coolant is decreased by an operation error or failureof the flowmeter, the protection unit determines an "abnormal flowrate". Then, the abnormality signal is sent to the operation controlunit arranged inside the electronic equipment to stop power supply tothe electronic components.

(2) When an abnormality of an electronic equipment is to be detected bythe temperature sensors, power supply to the electronic components isstopped upon detection of an abnormal temperature of one of theelectronic components. Therefore, even if the electronic componentitself is normally cooled, an "abnormal temperature" is determined uponoccurrence of an abnormality in one of the temperature sensors. Then,the abnormality signal is sent to the operation control unit inside theelectronic equipment, and the power supply to the electronic componentsis undesirably interrupted.

(3) Drawback (2) can be solved when determination reference for the"temperature sensor abnormality" is provided to determine the"temperature sensor abnormality" as described with reference to theprior art. However, even in this case, when the abnormal temperaturesensor value input to the temperature measuring unit 42 falls within therange between the abnormal temperature predetermined value and thetemperature sensor reference value, an abnormal temperature of anelectronic component is detected as in drawback (2), thereby undesirablyinterrupting power supply to the electronic components.

SUMMARY OF THE INVENTION

It is, therefore, a principal object of the present invention to solvethe drawbacks described above and to provide a cooling abnormalitydetection system having high reliability.

In order to achieve the above object of the present invention, there isprovided a cooling abnormality detection system for external electronicequipment, including a heat exchanger for performing heat exchange of aliquid coolant supplied from the external electronic equipment, acoolant tank for absorbing expansion of the liquid coolant supplied fromthe heat exchanger, a pump for supplying again the liquid coolant storedin the coolant tank to the external electronic equipment, and aprotection unit for detecting a cooling abnormality of the liquidcoolant in the electronic equipment. The operation control unit isarranged to stop the power supply to given electronic equipment when thecooling abnormality of the given electronic equipment is detected,thereby preventing reliability degradation or breakdown of theelectronic equipment, comprising, flow rate detecting means fordetecting a decrease in flow rate of the liquid coolant supplied fromthe electronic equipment, water level detecting means, arranged in thecoolant tank, for detecting a decrease in water level of the liquidcoolant, pump operation detecting means, arranged in the pump, fordetecting an operation of the pump, and abnormal temperature detectingmeans for detecting an abnormal temperature of the electronic equipment,wherein the protection unit discriminates the cooling abnormality whenthe abnormal temperature is detected by the temperature detecting meansduring the operation of the pump and discriminates the coolingabnormality when an abnormality is detected by any one of the flow ratedetecting means, the water level detecting means, and the abnormaltemperature detecting means during operation of the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a conventional cooling abnormalitydetection system;

FIG. 2 is a block diagram showing a first embodiment of the presentinvention;

FIG. 3 is a block diagram showing a detailed arrangement of a protectionunit shown in FIG. 2;

FIG. 4 is a flow chart showing an operation of the protection unit shownin FIG. 2;

FIG. 5 is a block diagram of a second embodiment of the presentinvention;

FIG. 6 is a block diagram showing a detailed arrangement of theprotection unit shown in FIG. 5;

FIG. 7 is a flow chart showing an operation of the protection unit shownin FIG. 5;

FIG. 8 is a block diagram showing a third embodiment of the presentinvention;

FIG. 9 is a block diagram showing a detailed arrangement of a protectionunit shown in FIG. 8; and

FIG. 10 is a flow chart showing an operation of the protection unitshown in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 2 is a block diagram showing a first embodiment of the presentinvention. The same reference numerals as in FIG. 1 denote the sameparts in FIG. 2. Reference numeral 12a denotes a protection unit; 21, awater level gauge arranged inside a tank 14; and 22, an eddy currentdetector arranged in a pump 15.

FIG. 3 is a block diagram showing a detailed arrangement of theprotection unit 12a shown in FIG. 2. Reference numeral 52 denotes aninformation measuring section 52; 53, an abnormality discriminationsection; and 54, an abnormality alarm section.

With the above arrangement, when a water level of the tank 14 becomesextremely low, the water level gauge 21 outputs an "abnormal waterlevel" signal to the protection unit 12a through an abnormalitydetection line 25a. The eddy current detector 22 outputs a signalrepresenting that the pump 15 is in an abnormal state to the protectionunit 12a through an abnormality detection line 25b. A flowmeter 23measures a flow rate of a coolant circulating during the operation ofthe pump. When a flow rate of the coolant becomes below thepredetermined value during the operation of the pump, the flowmeter 23outputs an "abnormal flow rate" signal to the protection unit 12athrough an abnormality detection line 25c. An "abnormal temperature"signal is output from the temperature measuring section 42 to theprotection unit 12a through an abnormal temperature signal line 33 inthe same manner as in FIG. 1.

As shown in FIG. 3, the protection unit 12a receives signals from theabnormality detection lines 25a to 25c and the abnormal temperaturesignal line 33. In this case, the protection unit 12a is operated inaccordance with a flow chart shown in FIG. 4. When the operation of theprotection unit is started, the protection unit determines whether thecooling device is in operation (step 101). If NO in step 101, theprotection unit 12a is set in the standby state. However, if YES in step101, the protection unit 12a determines whether the flow rate of theflowmeter 23 is a "low flow rate" (step 102). If YES in step 102, theeddy current detector 22 detects whether the pump 15 is abnormal (step103). If NO in step 103, the water level gauge 21 detects whether thewater level of the tank 14 is a "low water level" (step 104). If NO instep 104, the temperature measuring section 42 detects whether there isan abnormality in the temperatures of electronic components 43 (step105). If NO in step 105, the flow returns to step 101 (node A), and theabove operations are repeated.

However, if NO in step 102 the temperature measuring section 42determines a temperature abnormality of the electronic components 43(step 106). If NO in step 106, the flow returns to step 101. However, ifYES in step 106, the protection unit 12a drives an abnormality signalline 30 (step 107) to interrupt power supply to the electroniccomponents 43. The cooling device is stopped (step 108), and the flowreturns to step 101 again (node A). If YES in step 103 or 105, thetemperature measuring section 42 determines a temperature abnormality ofthe electronic components 43 (step 106). If YES is step 106; theprotection unit 12a is operated to drive the abnormality signal line 30if YES in step 105, the flow goes to step 107.

In the cooling abnormality detection system of this embodiment, theabnormality is detected by both the flowmeter and other associatedabnormality sensors or the like. Therefore, interruption of theelectronic equipment caused by an operation error of the flowmeteritself can be prevented with a higher probability. In the absence of thedetection of flow rate reduction, the abnormal state of cooling isjudged by detecting an abnormal temperature. When the flow ratereduction is detected, the abnormal state of cooling is judged bydetecting the abnormal state of the pump, low tank water level orabnormal temperature.

This embodiment can be used in a variety of applications. For example,when a coolant temperature adjustment heater is arranged in the tank 14,overheat of the heater (not shown) must be detected. In this case, trueoverheat can be discriminated only when an overheat temperature sensorgenerates an output, the actual water level of the tank 14 is detectedas a low water level, and an actual flow rate is detected as a low flowrate.

FIG. 5 is a block diagram showing a second embodiment of the presentinvention. Cooling of a liquid coolant flowing through electroniccomponents 43 is omitted in FIG. 5.

The same reference numerals as in FIG. 1 denote the same parts in FIG.5. Reference numeral 12b denotes a protection unit. The protection unit12b comprises a timer means 60 for counting a predetermined period oftime and outputting a time-out signal, a temperature measuring means 56for causing temperature sensors 44 to measure temperatures of electroniccomponents 43, a first abnormal temperature discriminating means 57,operated for the predetermined period of time set in the timer means 60,for discriminating one of the temperatures measured by the temperaturemeasuring means 56 as an abnormal temperature, a second abnormaltemperature discriminating means 58, operated after the predeterminedperiod of time set in the timer means 60, for discriminating between twoof the temperatures measured by the temperature measuring means 56 asabnormal temperatures, and an abnormality alarm means 59 for receivingthe abnormality signals from the first and second abnormal temperaturediscriminating means 57 and 58 and generating a stop signal through anabnormality signal line 30. The power source signal line 55 is used tosupply a power ON signal from an operation control unit 41 to the timermeans 60 and the temperature measuring means 56.

With the above arrangement, the temperature measuring means 56 receivesthe power ON signal from the operation control unit 41 to the electroniccomponents 43 through the power source signal line 55 and causes thetemperature sensors 44 arranged in the electronic components 43 tomeasure temperatures of the electronic components 43 during theiroperations. When the timer means 60 receives through the power sourcesignal line 55 the power ON signal, which indicates that the electroniccomponents 43 are being powered, the timer means 60 starts counting thepredetermined period of time. Each temperature measured by thetemperature measuring means 56 is input to both of the abnormaltemperature discriminating means 57 and 58.

Until the predetermined period of time is counted up by the timer means60, only the abnormal temperature discriminating means 57 is operated.Therefore, when one of the temperatures (temperature sensors 44) exceedsthe predetermined temperature, the abnormal temperature discriminatingmeans 57 detects an abnormal temperature. When this abnormal temperatureis discriminated, the abnormal temperature discriminating means 57outputs an abnormal temperature signal to the abnormality alarm means59. Upon reception of the abnormal temperature signal, the abnormalityalarm means 59 outputs the signal to the operation control unit 41through the abnormality signal line 30. Thereafter, the operationcontrol unit 41 interrupts power supply to the electronic components 43and prevents reliability degradation or breakdown of the electroniccomponents 43 caused by heat.

When the predetermined period of time counted by the timer 60 elapses,temperature measuring control is shifted from the abnormal temperaturediscriminating means 57 to the abnormal temperature discriminating means58. The abnormal temperature discriminating means 58 detects an abnormalstate when two of the temperatures measured by the temperature sensors44 are detected as abnormal temperatures. Upon detection of an abnormalstate, the same operations as those of the abnormal temperaturediscriminating means 57 are performed.

FIG. 6 is a block diagram showing a detailed internal arrangement of theprotection unit 12bA microcomputer system constituting the protectionunit 12b comprises a central portion consisting of a CPU 64, a ROM 65, aRAM 67, and an I/O port 68, a multiplexer 61 for selecting one of theplurality of temperature sensors 44, a preamplifier 62, and an A/Dconverter 63 for fetching temperature data to the CPU 64.

The ROM 65 stores programs necessary for control of the CPU 64 and datanecessary for abnormal temperature discrimination. The CPU 64 controlsthe multiplexer 61 to cause a selected temperature sensor signal to beinput to the preamplifier 62. At the same time, the CPU 64 causes theA/D converter 63 to convert the input signal from the preamplifier 62into digital data. The CPU 64 also controls the I/O port 68 to fetch apower supply start or stop signal representing the start or stop ofpower supplied from the operation control unit 41 to the electroniccomponents 43 through the power supply signal line 55. When an abnormaltemperature is detected, the CPU 64 supplies a power OFF command signalfor the electronic components 43 to the operation control unit 41through the abnormality signal line 30. The above control operations areperformed in accordance with software programs, and the necessarycontrol signals are supplied to the respective components to performabnormal temperature detection.

FIG. 7 is a flow chart-showing a control program of the protection unit12b. When the programs runs (step 201), the CPU 64 determines whetherelectronic equipment 40 is being powered (step 202). If NO in step 202,the timer means 60 is reset (step 203). The signal on the abnormalitysignal line 30 is disabled (step 204), and the flow returns to step 201for energization of the electronic equipment 40 (node B). However, ifYES in step 202, the CPU 64 determines whether the timer means 60 hasbeen started (step 205). If NO in step 205, the CPU 64 starts the timer60 (step 206). However, if YES in step 205, step 206 is omitted. One ofthe plurality of temperature sensors 44 is selected (step 207), and atemperature measurement is performed. The measured temperature isfetched by the temperature measuring means 56 (step 208). The CPU 64determines whether the predetermined period of time (e.g., 1000 sec.)set in the timer means 60 has elapsed (step 209). If NO in step 209, theCPU 64 determines that an abnormal temperature is detected by onetemperature sensor (i.e., one electronic component) (step 210). However,if YES in step 209, the CPU 64 determines whether abnormal temperaturesare detected by two or more temperature sensors (i.e., two electroniccomponents) (step 211). If NO in step 210 or 211, the flow returns tostep 201 to perform the next temperature measurement (node B). However,if YES in step 210 or 211, the CPU 64 supplies a power OFF commandsignal to the operation control unit 41 through the abnormality signalline 30, so as to stop the power supply to the electronic components 43(step 212). The flow then returns to step 201 (node B).

In the cooling abnormality detection system for electronic components ofthis embodiment, when the predetermined period of time elapses from thepower-on timing of the electronic equipment 40, the discriminationoperation is switched from the abnormal temperature discriminating means57 for discriminating one abnormal temperature to the abnormaltemperature discriminating means 58 for discriminating two or moreabnormal temperatures. Therefore, even if, e.g., one temperature sensoris broken, the abnormal temperature discriminating means 58 does notdiscriminate an abnormal state, thereby preventing an operation errorcaused by a temperature sensor failure.

Since two abnormal temperature discriminating means are provided, theabnormal temperature discriminating means 57 discriminates an abnormaltemperature caused by an initial abnormality (e.g., a mounting or fixingerror of a flat plate of the liquid coolant during exchange at the timeof repairing of electronic components) requiring an immediate halt ofpower to electronic equipment 40. At the same time, when thepredetermined period of time elapses from power-on of the electronicequipment 40, the abnormal temperature discriminating means 58 candiscriminate an abnormal temperature of the electronic component 43 overa long period of time for which an operation error of the temperaturesensor is not allowed.

The above embodiment exemplifies an arrangement in which the temperaturesensors 44 are arranged in the electronic components 43, respectively.However, a plurality of temperature sensors may be arranged in eachelectronic component.

FIG. 8 is a block diagram showing a third embodiment of the presentinvention. Cooling of a liquid coolant flowing through electroniccomponents 43 is omitted as in the second embodiment. The same referencenumerals as in FIG. 1 denote the same parts in FIG. 8. Two temperaturesensors 44 are arranged in each electronic component 43. Referencenumeral 12c denotes a protection unit for protecting the electroniccomponents 43 from abnormal temperatures; and 70, a temperaturemeasuring means. The temperature measuring means 70 causes thetemperature sensors 44 to measure temperatures of the electroniccomponents 43 during power supply from an operation control unit 41 tothe electronic components 43 through a power source signal line 55. Themeasurement results of the temperature measuring means 70 arediscriminated by a temperature/temperature difference measuring means71. The temperature/temperature difference measuring means 71 comparestemperatures detected by the two temperature sensors 44 of eachelectronic component 43 with a reference temperature and discriminateswhether a difference between the two measured temperatures falls withinan allowable range.

For example, if a measurement error of the temperature sensor 44 usedfalls within the range of +2° C., an absolute value of the differencebetween the measured values of the two temperature sensors 44 is amaximum of 4° C. Therefore, the temperature/temperature differencemeasuring means 71 discriminates whether the absolute value of thedifference between the measured temperatures of the two temperaturesensors 44 is a maximum allowable error of 4° C. or less. When theabsolute value of the difference between the measured temperatures ofthe two temperature sensors 44 exceeds the allowable error, thetemperature/temperature difference measuring means 71 detects anabnormality of the temperature sensor 44 or a temperature detectionsystem, and supplies an abnormality signal to a sensor failure alarmmeans 73. Thereafter, the sensor failure alarm means 73 supplies anabnormality signal to an abnormality monitor unit 69 through anabnormality signal line 30a. The abnormality monitor unit 69 signalsoccurrence of an abnormality to maintenance personnel (not shown). Whenthe absolute value of the difference between the measured temperaturesof the two temperature sensors falls within the allowable error and themeasured values exceed the reference temperature, thetemperature/temperature difference measuring means 71 transmits anabnormality signal to the abnormal temperature alarm means 72.Thereafter, the abnormal temperature alarm means transmits anabnormality signal to the operation control unit 41 through theabnormality signal line 30, and then the operation control unit 41interrupts power supply to the electronic components 43.

FIG. 9 is a block diagram of an arrangement of the protection unit ofthis embodiment using a microcomputer system. The protection unit 12ccomprises a central portion consisting of a CPU 78, a ROM 79, a RAM 80,and an I/O port 81, a multiplexer 74 for selecting one of the pluralityof temperature sensors 44, a preamplifier 75, a sample/hold circuit 76,and an A/D converter 77 for fetching temperature data into the CPU 78.

The ROM 79 stores programs necessary for control, and data required forabnormality discrimination for hardware consisting of the abnormaltemperature discrimination/temperature sensors 44, a cable forconnecting the temperature sensor 44 and the multiplexer 74, thepreamplifier 75, the sample/hold circuit 76, and the A/D converter 77.The CPU 78 controls the multiplexer 74 and multiplexer 74 transmits asignal of the selected temperature sensor 44 to the preamplifier 75. Atthe same time, the CPU 78 controls the sample/hold circuit 76, andsample/hold circuit 76 and holds an output value from the preamplifier75 and transmits it to the A/D converter 77 at an arbitrary timing. Inaddition, the CPU 78 controls the A/D converter 77 to convert an inputfrom the sample/hold circuit 76 into digital data. The digital data isfetched by the CPU 78. The CPU 78 controls the I/O port 81 to fetch apower start/stop signal from the operation control unit 41 and drivesabnormality signal lines 30 and 30a during abnormal states such astemperature abnormal state, a temperature sensor abnormal state, and atemperature detection system abnormal state. These control operationsare performed in accordance with software programs, and the necessarycontrol signals are supplied to the respective components, therebyperforming abnormality detection operations such as an abnormaltemperature detection, a sensor failure detection, and a temperaturedetection system failure detection.

FIG. 10 is a flow chart of a control program showing the aboveoperation. When the program runs, the CPU 78 determines that theelectronic equipment is powered (step 301). If NO in step 301, theabnormal signal lines 30 and 30a are disabled (step 310), and the flowreturns to step 301. However, if YES in step 301, the CPU 78 causes themultiplexer to select the first temperature sensor of one of theelectronic components (step 302). A temperature measurement of the firsttemperature sensor is performed, and the measurement result is fetchedby the CPU 78 (step 303). The second temperature sensor of the sampleelectronic component is selected by the multiplexer (step 304), and atemperature measurement is performed (step 305). The CPU 78 thendetermines whether an absolute value of a difference between themeasured temperatures falls within the allowable error (step 306). If NOin step 306, a sensor failure (including a failure of the temperaturedetection system) is signaled through the abnormality signal line 30a(step 309), and the flow returns to step 301 (node C). However, if YESin step 306, the CPU 78 determines whether both the measuredtemperatures are abnormal temperatures (step 307). If NO in step 307,the flow returns to step 301 (node C). However, if YES in step 307, theabnormality signal line 30 is driven (step 308), and then the flowreturns to step 301 (node C).

In the cooling abnormality detection system of this embodiment,temperatures of each electronic component are measured by twotemperature sensors, and the abnormal temperature is discriminated onthe basis of the measured temperatures and the difference between themeasured temperatures. Therefore, a detection error of an abnormaltemperature which is caused by a failure of the temperature sensoritself or the temperature detection system can be prevented with a highprobability.

What is claimed is:
 1. A cooling abnormality detection system forexternal electronic equipment, including a heat exchanger for performingthe heat exchange of a liquid coolant supplied from the externalelectronic equipment, a coolant tank for absorbing expansion of theliquid coolant supplied from said heat exchanger, a pump for circulatingthe liquid coolant stored in the coolant tank to the external electronicequipment, and a protection unit for detecting a cooling abnormality ofthe liquid coolant in said electronic equipment, said protection unitbeing arranged to stop the power supply to a given electronic equipmentwhen the cooling abnormality of said given electronic equipment isdetected, thereby preventing reliability degradation and breakdown ofsaid electronic equipment, said protection unit comprising:temperaturemeasuring means for detecting the temperature of said electronicequipment while said electronic equipment is being powered; timer meansfor starting counting a predetermined period of time when saidelectronic equipment is powered and for outputting a signal when thepredetermined period of item elapses; first abnormal temperaturediscriminating means, which operates until a time-out signal is outputfrom said timer means, for discriminating whether one temperaturemeasured by said temperature measuring means is an abnormal temperature;second abnormal temperature discriminating means, which operates afterthe time-out signal is output from said timer means, for discriminatingwhether a plurality of temperatures measured by said temperaturemeasuring means are abnormal temperatures; and abnormality alarm meansfor receiving an abnormality signal from at least one of said first andsecond abnormal temperature discriminating means for stopping the powersupply to said internal electronic equipment.